Global Land Use

I've been continuing with my slow meandering efforts to understand the large facts about the biosphere, and thus it's potential for things like making biofuels as well as sequestering (or releasing) carbon, etc. This post is a small milestone along the way: I just wanted to put up a few graphs of what humanity uses the globe for (as you'll see, humanity is already using most of the land area).

Major classes of global land use shown as stacked areas. Source: FAO.

In this post, I'll work in units of billions of hectares. A thousand hectares is 10 square kilometers, or 3.86 square miles. The land area of the planet is 14.8 billion hectares. Of that, 1.4 b.h. is Antarctica which has a rather low biological productivity. That leaves 13.4 b.h. or so in the rest of the continents. The top ten countries in terms of land area in these units are:

United States0.96

These ten countries represent 53% of the non-Antarctica land area. If the European Union was a country, it would weigh in at 0.40 b.h. - slightly ahead of India, but far behind the bigger countries.

According to the FAO, the recent trends in global land usage are as follows.

Major classes of global land use shown as stacked areas. Source: FAO.

As you can see, it adds up to about the 13.4 b.h. expected. Unfortunately the data series for forests/woodlands and "All other land" end in 1994. These are the largest categories, with pasture land a little bit behind, and then arable land somewhat smaller and permanent crops (eg orchards, sugar cane) far behind again.

It's easier to get a sense of the trends (which are fairly slight) in individual classes by looking at a line graph:

Major classes of global land use shown as individual trend lines. Source: FAO.

There are steady but modest decreases in forests and other lands, and steady but modest increases in pasture land and arable land. Presumably, these trends are likely to continue as human population increases. But it's hard to see them radically accelerating, given that people are already using almost all the best land. Thus major changes in the production of the land would have to come from changing the productivity of it, not from expanding the area utilized.

Finally, the FAO has statistics of agricultural land (arable plus pasture plus permanent crops) that is irrigated. Here's what that graph looks like:

Percentage of arable land that is irrigated. Source: FAO.

As you can see, it's been going up pretty steadily, except for a leveling off in the last few years. Whether that leveling off is a temporary matter or something more serious, I don't know. I've been reading Lester Brown's Plan B lately; he's very concerned about water, but he doesn't present the evidence clearly enough for me to decide whether I agree with him or not.

I may be misreading the graph.....what event caused the drop in woodland circa 1995?  It appears like 80% of the worlds forest went to other use.  Am I misreading this?  I know there has been rain forest depletion but the US is covering more acreage every year with forest.  Whats up?
The FAO data series for forest and "all other land" end in 1994.  So we don't know what happened after that.  (But it presumably wasn't too radical, or it would have had to show up in the agricultural land.
One problem with subtracting the Antarctic landmass from the global land area to get 13.4 billion ha. is that the resulting total includes a lot of mountaintops and deserts with insignificant productive value. Down below, Jason Bradford points out that ecological footprint analysis is another way of approaching this issue. The analysis at includes a methodology paper saying:
Globally we identify 11.2 billion hectares of distinct bioproductive areas--cropland, forest, pasture, fisheries, and built-up land--that provide economically useful concentrations of renewable resources. These 11.2 billion hectares cover a little under one quarter of the planet and include 2.3 billion hectares of marine and inland fisheries and 8.8 billion hectares of land. The land area is comprised of 1.5 billion hectares of cropland, 3.5 billion hectares of grazing land, 3.6 billion hectares of forest, and an additional 0.2 billion hectares of built-up land assumed to occupy potential cropland  

They estimate that these 11.2 billion ha capture at least 80-90% of the total usable annual generation of biomass.

The site includes a couple of figures showing the decline over time in biological capacity, due mostly to resource depletion and ecosystem degradation, and in the area occupied for agricultural crops.  While data supporting the early part of the analyses are less reliable, the overall trends are probably more realistic than the ones above, which are based on incomplete data from the FAO.

Good point. Paving some of the nastier / less productive desert land in the foot hills of North Scottsdale is probably a lot less damaging that paving an equivalent acrage of prime agricultural land. Location, locations and location aren't everything ... there is also top soil, water and growing season length.
1 hectare is an area 100 m x 100 m; therefore, there are 100 ha in 1 km2
You say "A hectare is 10 square kilometers, or 3.86 square miles". Hmm isnt it 100x100m , 0.1 km2, see Wikipedia Or you've got a bigger unit in the US than we europeans even for land :) ciao
Yeah that was my first thought aswell, a hectare being 100m x 100m which is actually 0.01 km2 (0.1 km x 0.1 km) i.e. 100 hectares per square kilometer (and 259 hectares per square mile).
BTW I think the actual figures quoted are correct, just the conversion factor stated wrong. ie. SS states the land area of the planet is 14.8 billion ha (divide by 100) = 148 million km2 which is correct.
Mea culpa - the FAO figures from the source are in thousands of hectares, which is 10s of km^2, but I mis-stated it in the piece.  I've fixed it.
IMHO Energy is a far more important issue than water. You use water, but burn fossil fuels.

Moreover, the Oil Civilization in fact has no water, it just spends a bit more energy in treating and bringing water to the big cities.

Being in England with an 18 month on going drought and potentially water stand pipes in the streets this summer, I am not so sure that energy is more important than water. At an extreme, no water or highly polluted water means you die in about a week (depending on climate etc), having no oil, just means returning to a basic life that has existed for most of history. I feel you can get by without oil, but you can't get by without water or at least useable water for agriculture and drinking. I am not sure if there is a shortage of good water or increasing use/wastage of water from a fixed supply in the world.
"Water" is a lot more complex than just the stuff that comes out of your faucet.

Coming to grips with "water" is probably as much an effort as learning about Peak Oil except that water is not burnt and thereby chemically converted into a GreenHouse Gas like CO2 (not to say that H2O is not a GHG itself, which it is.) Thus "water" can theoretically be recycled, which makes it sound like it's no big deal. It is a big deal. Wars are fought over water.

Jared Diamond's book, "Collapse" discusses how water can bring a civilzation to its knees.

This is a good place to continue my quantitative analysis of the absurdity of using biofuels - not to save human lives - but to save the 700 million private automobiles that are the dominant lifeform on this planet and other forms of unecessary high energy consumption.

The best case wet tropical environments have a net primary productivity of 9000kcal/year with yielded an estimate of 160m2 to grow a barrel of oil.  I was asked for a more realistic case.  Well, the best case palm oil plantations are said to produce 7250 litres/hectare/year.  (No, I don't know how much fossil fuel fertilizers and chemicals are needed in the process)  This is close to a limiting case where almost 3/4ths of the net primary productivity goes into palm oil production.  So allowing for a few roads and barracks you could grow replacement for fossil fuels on "only" 15 million km2.

The trouble is that this exceeds 10% of the land area of the planet, and only wet tropical land will grow palm oil.  In fact it is nearly double the entire area of Brazil.  So only by destroying the entire tropical belt ecosystem (goodbye Amazon, Congo, Borneo) and genocide of the native populations (in excess of the slaves needed to work the palm oil plantations) would it be even in rough theory possible to grow even one crop of biofuels equivalent to fossil fuel use.   I don't know what soil fertility of a palm oil plantation is like after years of harvesting this monocrop, but doubt it improves over time.

Rich baby boomers can relax, they should be able to get petrol enough to drive their 200 horsepower cars (think about that, this implies that your car should need 200 times as much land to grow food as a horse does!) until they retire.  But please don't delude yourselves that your grandchildren will be able to do the same with biofuels.   Here is the future of biofueled personal transportation: bicycle  (maybe with small motor assist) for most folks, oxcarts on the farm, and for the rich folks a horse carriage to go into town

EDIT 9000kcal/m2/year is best net primary productivity - (I left out the m2)
It's better than that; we should be able to run plug-in hybrids indefinitely.  If we take the billion-ton biomass  (per year) claim at face value and postulate that we can get between 50 and 80 gallons of ethanol per ton, that's 50 to 80 billion gallons of ethanol per year.  The US currently burns about 200 billion gallons of motor fuel per year; plug-in hybrids appear to be able to cut liquid-fuel needs by as much as 80%, so that plus ethanol from biomass put us in the neighborhood of indefinite sustainability.

However, there is NOTHING we can do if we allowed continued population growth through immigration.  And that includes not just transportation, but food production, housing, land preservation and everything else.

But if you harvest biomass at anything like that sort of rate, the ecosystem collapses fairly rapidly. You need to recycle a lot of it in order to preserve soil fertility, and leave lots more of it in place to stop the soil from eroding. Take too much and you end up with the Oklahoma dustbowl, but on a global scale, and with nowhere else to migrate to.
We're already harvesting a great deal of that (municipal green waste, etc.) but not using it effectively.  Further, a lot of what isn't technically harvested (crop wastes) contributes little or nothing to soil tilth because it rots on the surface and never penetrates.

We have examples of processes which turn waste biomass into charcoal and fuel gas (which could feed Clostridium cultures to make liquid fuel), and we also have existence proofs of long-term sequestration of carbon and enhancement of soil properties by addition of charcoal to soil.  We can get energy from biomass, enhance soil fertility and pull carbon out of the atmosphere; they are not mutually exclusive.

Where will you get the additional electricity for your plug-in hybrid? That'a a lot. Coal? only if you're willing to accelerate Global warming and further degrade air and water.  Wind? A little. Solar? A little? Nuclear? Better start building pretty soon, because it takes a long time to develop that much additional capacity. We will need to do a lot simply to replace the electricity and space heating we now get from natural gas and space heating from oil.

Don't misunderstand. I am in favor of plug-in hybrids at an indvidual level. (I want one, and I plan to build a home/farm wind-power station.) But it doesn't create any new energy. If we move as much weight as many miles, we'll need a LOT more electricity to do it.

It doesn't create any new energy but it allows you to do the same thing with a lot less.

Here's a paper that compares the relative "door to door" efficiency of gasoline vs. electricity:

Where will you get the additional electricity for your plug-in hybrid? That'a a lot.
Not really.  Depending on the efficiency of current vehicles, we might get by with as little as 81 GW of power delivered to the wheels (assuming 15% tank-to-wheels efficiency and no improvements in vehicle energy requirements... which are certainly going to happen if prices stay high).  Solar PV through batteries is roughly competitive with gasoline now; cheaper solar (better PV or alternate tech like Stirlings) and better batteries will make it pay to convert.  The great thing is that anything which makes more clean electricity helps, no matter what it is.

Annual US gasoline consumption is about 140 billion gallons; if we assume 22 MPG average, that's 3.08 trillion vehicle-miles.  If we can drive 80% of that on electricity at 350 Wh/mile average, we'd need 862 billion kWh/year or around 22% of current US electric consumption; call it 98 GW average.  If we added wind capacity at 20 GW/year and got 30% capacity factor, we'd add 6 GW/year average from wind.  Wind would fill the electric demand from vehicles after about 17 years, which just happens to be the average lifespan of passenger cars in the US.

Note that the available wind power on the US continent is around 1.2 terawatts.

There are some issues which would have to be resolved to make this actually work minute-by-minute, but the broad level details of how much energy is available and so forth lead inevitably to the conclusion that this can be done.  You can have your Hummer as long as it runs on Li-ion cells.

Where will you get the additional electricity for your plug-in hybrid?

How about starting with the corn current going into ethanol production? One bushel of corn is used to produce 2.6 gallons of ethanol at 77000 BTU per gallon generates about 200000 BTUs. That corn contained ~400000 BTUs. If instead you took the corn to a power plant and used it to generate electricity you could power two plug-in hybrids with the corn used to power one E85 vehicle.

"However, there is NOTHING we can do if we allowed continued population growth through immigration."

Unless one believes in gray aliens from Zeta Reticuli, there is no immigration.  The earth is a spherical system which can be considered closed except that it absorbs sunlight and emits infrared.  Climate change, peak oil and overpopulation are not easily contained by political barriers.

Immigration from where?  Are these new folks coming from off planet, or something?  Or are you seriously proposing that we in American should (or can) preserve our way of life while the rest of the world collapses into chaos?

Peak energy, peak food, peak water: these are global problems.  The solutions will be global over the long term, or they won't be solutions at all.

Are these new folks coming from off planet, or something?
I'm sure many, including lots of Christians, would say yes. ;-)

They're coming via the same route that we all did:  they were born.  But we can't force other regions of the world to make the changes to deal with their own overpopulation if we keep taking it off their hands.  "Think globally, act locally."

The parts of the world which still have high rates of population growth send very few emigrants to the US.
You mean, Mexico sends fewer people to the US than Sweden?

Excuse me while I roll on the floor laughing.

You mean, Mexico sends fewer people to the US than Sweden?

Excuse me while I roll on the floor laughing.

Mexico's rate of population growth is no longer high by world standards. Think of sub-Saharan Africa (except the southern tip), the Middle East (except Lebanon and Israel), Pakistan and the north Indian plain. Those populations are all growing at well over 2% a year, which Mexico no longer is.
Biodiesel from algae is 10 times better than this per area.  You can use seawater on non-arable land like desert.  Check into it at
This could save the day if we get our rears in gear.
This could save the day if we get our rears in gear.

Several thoughts:

  1. This has not been done on anything but a very small scale

  2. When we talk about an EROI (Energy Return on Investment), we usually assume its solely a return on Energy invested, but there are many inputs to an energy process: energy, land, water, labor, etc. So the EROEI may be very high for algae to oil but the water and land costs could be enormous making the scalability of it small

  3. Any alternative energy that has a huge energy payoff puts us in the dangerous position of creating more energy and thus more leverage for humans to build, buy, burn and excrete more stuff. We really are running up against environmental constraints, global warming being one of the more prominent but possibly not the greatest threat (food supply, ocean health, toxicity, etc). For a 20-30:1 new energy process to replace oil and gas may seem a boon on the surface, but the externalities of such a boon must be accounted for. This doesnt make the process itself bad (algae to liquid fuel) but what we do with the net energy gain.

As Lee Corso on ESPN says...."Not so fast my friend"..
Someone else famous said "Be careful what you wish for, you might get it"
Until they address the problem of turning the desert into salt flats, I'm disinclined to take this proposal seriously. They mention that evaporation is a problem, but don't even hint out how to address it.
Using closed bioreactors solves the evaporation problem. The main issue is finding a cheap tranparent material.

as reported in Scientific American

Using closed bioreactors creates the problem of acquiring the carbon, since you no longer have gas exchange with the atmosphere.

The solution is to use halophilic algae and just let the water evaporate; exchange with seawater to maintain the optimal salt concentration.

A couple of immediate reactions.

The first graph is labelled "Flows of carbon in biomass products..." but this does not match the graph.

"as you'll see, humanity is already using most of the land area "

Maybe I missed something, but I don't see where that is justified? It obviously depends on what is meant by "using", but it looks to me we are using perhaps 50%.

I don't what the FAO definition is, but the figures look more like how land is allocated. Land may be forested, but that doesn't necessarily mean it is being actively logged.

As you point out, the acreage doesn't mean much by itself, you also need to consider intensity of land use, which is probably a better metric. I think it is instructive to also look at Net Primary Production for example.

I fixed the bad label.  I'll talk more about the degree to which we are or aren't using the planet in a future post.
Looking at land use after failure in our/world economy I have wondered the overall effect people putting in small gardens in their yards. The Victory gardens of the past will happen with energy scarcity and make so much sense.

The two major increases in farmland have been due to the tractor and irrigation. My memory is the big arable land increases happened in the 70's. A good deal of this land is considered maginal & irrigation I imagine is the limiting factor.

So maybe gains in land-gardens, but larger size losses-land requiring irrigation. Add in global warming and rain loss for some of the Breadbasket of the world and I get concerned even for the US. Of course this would be disastrous for the grain importers.

I am skeptical about biofuels because I believe energy losses/EROEI would be so evident only military & the rich would attempt such & social disorder would be the bigger issue.

I was supprised at the percentage of irrigated land - I figured it would be much higher.  Currently we are irrigating less then 6% of the land, but it has resulted in major problems.  We are depleting aquifers, draining lakes and rivers, and salinating the farmland.  As a supplement in an area that doesn't get enough rain fall it is fine, bu large scale irrigation is not sustainable.

As we go through the dual effects of PO and GW we will see less production from our current ag land - less fuel for equipment, less manufactured fertilizer, less pesticides and less energy for irrigation.  Throw in changes in weather patterns because of GW and you could have areas that are currently producing crops loose their water supply or have their rainfall amounts decreased to where they do not produce at the same levels.

Stuart was looking at ways to get energy out of the biosphere and sink CO2 into it.  I don't think we are going to see great changes - increases anyway - in the amount of energy produced by our arable land or permanent pastures.  These lands are already producing about as much as they can with traditional methods.  If we are going to increase we need to reach into the 'other lands' with no traditional methods to gather energy - solar, wind, biofuel from alge.  

I don't think we can afford to 'try' something new with our arable land right now, not until we find more sustainable ways of producing from that land.  Then again, we may come to a point in the future where we cannot afford to not 'try' something new.

One last thing that I see in this information is that things do not change all that much over the past 40+ years, but we are getting more out of our arable land.  What happens when that arable land starts going back to 'other land'?


For a more in-depth look at patterns of global land-use, check out this article by Foley et al. (2005) in Science. id=sci

Could you please post the article? I do not have a suscription to Science nor can I afford it!!
Since the ASPO numbers show a Natural Gas peak around 2011 (just 5 short years away!), and since the cost of fertilizer is 70% to 90% due to Nat Gas, will "peak food" occur around 2011? Or sooner if tar sands continues to ramp up?
Have a look through this report on global grain markets.

Logistical peak food seems to be upon us.  Since 2000, the trend is for consumption to be greater than production.  We have significant stores, which we are now eating down.

This article says that the global food pantry has dwindled from 116 days in 2000 to 69 now, and may be just 57 days by year's end.

The president of Canda's National Farmer's Union has written this letter to Kofi Annan regarding this alarming decline.

Don't worry, it's only Toyota's JIT (just in time) philosophy carried over to grain. What do you consider a good number of days inventory? 116? 5? 365 x 7 for a biblical famine?
I dunno.  But the way I see it, we're now consuming more than we produce - just like oil.  Constraints are several - aquifers are being depleted, soil is being lost and damaged, fertilizer is becoming more dear, and available arable land is about maxed out.  There's nowhere to turn to up production as we've always been able to do in the past. So we're hanging our hat on GM crops - frankenfood - which apparently, from the trend, cannot make up the difference.  Again, I dunno.  But I suggest keeping an eye on this trend.  If it bottoms out at something around zero, then I guess it's just JIT economics.  I think it's much more dire than that, and sometime in about 5 years, it goes below zero.  Peak everything, at about the same time....
I sort of agree with JN2 here. An example is Corn prices which have ranged between $2.00 and $2.50 for most of the time since 1998. Soybeans were below $6 most of that time (with one big spike). Wheat was in an uptrend from $2.50 to $4.00 over that timeframe (that's 6% per year). Why would we inventory this stuff if it isn't going up in value? Was output of these crops limited by scarcity of some input? Are inputs currently scarce?

My question is really about substitutes for fertilizer. If we predict that fertilizer will be increasingly scarce in the future, what are the substitutes? Do they scale up? Or what current demand for natural gas, which is used to create fertilizer, will be forgone?

How much anhydrous ammonia do the Amish buy? My guess is zero yet they still run successful, highly productive farms without the use of fossil fuels. What's the EROEI if I only use Amish corn and a solar still?
Land utilization from algae based oil production is 10 times more efficient than producing corn based ethanol. OD doesn't support tables so I have the table here:

Algae based Biodiesel vs. Cellulosic Ethanol

We would need more land than the USA has to produce enough ethanol. The desert and salty lakes are a great place to grow algae.

There is plenty of fresh water if you count the Greenland and Antartic ice caps,but these locations are'nt close to the areas that need water for irrigation. And water require energy for pumping, desalinization.
   The United States has plenty of unutilised fallow farmland. But the energy return on planting crops for alcohol is marginal. So the only good answer is limiting the size of families to no more than two children which is below the replacemnt rate and giving up two cars per family. Not an easy sell. Six billion people is above the long term carrying capacity of our planet no matter what the Pope says
I've read Plan B 2.0
I was a bit disappointed as well, Stuart.  Although
I was impressed with Lester's knowledge of
agriculture and water.  His understanding of
economics is limited (in my view).
Have you ever looked into the Ecological Footprint analyses.  I'd love to get your impression.  There are two organizations doing these, and one just came out with a new study:  is a really great way to take a tour of nations and compare their footprints.  I was amazed that the US footprint is over 5 times our national biocapacity!  This implies that to live within the resources of our nation (and to therefore adhere to the now popular cry of weaning us from our addiction to foreign oil) would minimally require a reduction in our resource consumption and pollution levels to a fifth of what they are today.  

I interviewed the author of this report on May 8th and it can be found here:

FYI, I interview Nate Hagens (thelastsasquatch) this Monday. Streaming from 9-10 PDT.

Jason - thanks for the heads-up on Nate.  I live 30 miles north of you and get KZYX.

A general comment - the fact that social, economic, governance and population transitions have not begun leads me to remain highly pessimistic as to the future.  I started my own transition 30 years ago and my expectation is that society will panic and make all the wrong choices attempting to maintain the status quo.

I think you may be right, but I am doing my best to try for another outcome.
I once heard a Sierra Club representative during a debate about California water policy assert that irrigation lead to transiant societies.  Was that true?

The definitive book on the subject is Wittfogel's "Oriental Despotism."  He make a strong case that irrigation-based societies have in historical times been remarkably stable and powerful.  Think Egypt.  The reason is that irrigated land offered a solid and reliable EROEI.

The increase in irrigated acrage post-WWII has been due to exports of "pre-packed" energies from industrial societies to Third World countries.  In ancient times, a society had to be able to bootstrap themselves into a fancy irrigation system by saving and reinvesting excess labor into dams and canals.  Nowadays, we rich countries give them away.

Can we increase irrigated acrage?  Probably not since we've reached a point of declining returns worldwide and certainly within the US.

As to the source of Stuart's statistics (the FAO), do you have alternate sources to check the UN figures?  I've heard other statements that we've plenty of unused land worldwide.

Not directly on topic, but some time back I ran into a couple of interesting factoids regarding total planetary biomass:

99% of biomass is in plants, vs animals or microorganisms.
99% of plant biomass is in land plants, vs ocean plants.

I was surprised that plants are so dominant over animals in biomass. We often think of plants as something of an evolutionary dead-end, that animals have taken over, but in fact animals are almost negligible in the big picture.

I also had always thought of the oceans as being fertile, being where life originated and all, but actually I guess most of them are essentially deserted of life. The land adaptation really was a major evolutionary step forward.

Got this info from a forestry site of all places:

There's a distinction between standing biomass and what is called biological productivity.

A pond full of algae can have low algal biomass and be constantly eaten by fish, but have high productivity, meaning how much carbon and energy is captured and turned into living tissues.  

Aquatic systems tend to have low standing biomass but can have high productivity.

On land, the fertile grasslands have high productivity and low standing biomass and are eaten by very big herds, e.g. ,bison and wildebeast.

If you want to think if it in terms of oil, you can have a small reservoir under high pressure with a fast rate of extraction or something like the tar sands, which are huge but have a low rate of extraction.  But this is not a great analogy since these are non-renewable and will run out.  Ecosystems don't tend to have that problem if left alone.

I wonder if it will ever be feasible to farm algae from vast areas of the ocean - especially areas that have relatively low average wind/currents, like the "Doldrums". The harvesting/tending could be done by small robotic ships that collect the algae & transport it back to a mother ship where it is processed using solar energy to produce food and fuel.
I think the savings from backyard gardening are exaggerated. Bulk grains (bread, rice), dairy, red meat and out-of-season veg are beyond suburban quarter-acre plots. Particularly if there are constraints to tap water usage. Home gardening is more of a feelgood activity where you don't have to drive into town to seek entertainment. It augments the low wattage light bulbs ethos but it won't undermine the industrial agricultural base.  We'll always need megatons of fertiliser and heavy machinery. Somehow we need to figure how to maintain this core of industrial agriculture with minimal fossil fuel inputs.

I don't inherently disagree.  However, a significant amount of food, including meat (rabbit, chicken, fish) can be produced using a variety of techniques.

Find a copy of The Integral Urban House, ISBN 0-87156-213-8 for lots of details on growing food at home.  For an overview, see:

I didn't check to see if the link still works.

I would also suggest Post Soviet Lessons for a Post-American Century:

where the value of the kitchen garden is shown.

People may not be able to produce all their food but anything may keep them from starving.  Do I expect them to do it?  No.

In Ruanda before their civil war the average "farm" was less than 2 acres in size, and these farms supported large families in abject poverty. The end result was the Hutu and Tutsi cut a whole lot of each other's heads off with machetes and the UN sent in food. How about just restricting our reproduction and not spending every last dollar on automobiles? Conservation and birth control work, but it must start with us.
Wouldn't it be optimal to import those bulk dry goods (flour, rice, beans, ...) from out of area, and then garden those fresh vegetables that are so much less efficient to deliver?

If nothing else, you stop shipping the water weight of fresh vegetables by truck (and sometimes air!).

That is an excellent point.  Would e.g. condominium rules allow people to put little hydroponic troughs on their roofs and use that area productively?
A lot of people have patios or balcanies which makes it easier, of course.  And for those that don't, don't forget the sprouts.